ML17311A702

Forwards Engineering Evaluation of Auxiliary Pressurizer Spray, Addressing Util Position That Current CVCS Configuration,Including Auxiliary Pressurizer Spray Sys Satisfactory & Capable of Mitigating Licensing Basis

ML17311A702
Person / Time
Site:	Palo Verde
Issue date:	03/09/1995
From:	Stewart W ARIZONA PUBLIC SERVICE CO. (FORMERLY ARIZONA NUCLEAR
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
Shared Package
ML17311A703	List: ML17311A702
References
102-03278-WLS-A, 102-3278-WLS-A, NUDOCS 9503160316
Download: ML17311A702 (8)

Text

P R.IC3RIMY' (ACCELERATED RIDS PROCESSIN REGULATORY INFORMATION DISTRIBUTION., SYSTEM (RIDS)

ACCESSION NBR:9503160316 DOC.DATE: 95/03/09 NOTARIZED: NO DOCKET FACIL:STN-50-528 Palo Verde Nuclear Station, Unit 1, Arizona Publi 05000528 STN-50-529 Palo Verde Nuclear Station, Unit 2, Arizona Publi 05000529 STN-50-530 Palo Verde Nuclear Station, Unit 3, Arizona Publi 05000530 p

AUTH.NAME AUTHOR AFFILIATION STEWART,W.L.

Arizona Public Service Co.

(formerly Arizona Nuclear Power RECIP.NAME RECIPIENT AFFILIATION R

Document Control Branch (Document Control Desk)

SUBJECT:

Forwards "Engineering Evaluation of Auxiliary Pressurizer Spray," addressing util position that current CVCS configuration,including auxiliary pressurizer spray sys 0

satisfactory

& capable of mitigating licensing basxs.

DISTRIBUTION CODE:

AOOID COPIES RECEIVED:LTR 2 ENCL

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SIZE: 3 + I2C R

TITLE: OR Submittal:

General Distribution NOTES:STANDARDIZED PLANT Standardized plant.

Standardized plant.

RECIPIENT ID CODE/NAME PD4-2 LA HOLIAN, B INTERNAL: ACRS NRR/DRCH/HICB NRR/DSSA/SRXB OGC/HDS2 EXTERNAL: NOAC COPIES LTTR ENCL 1

1 1

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1 NRR/DSSA/SPLB NUDOCS-ABSTRACT NRC PDR COPIES LTTR ENCL 1

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NOTE TO ALL"RIDS" RECIPIENTS:

PLEASE HELP US TO REDUCE WASTE! CONTACTTHE DOCUMENTCONTROL DESK, ROOIPI PI-37 (EXT. 504-2083 ) TO ELIMFNATEYOUR NAMEFROM DISTRIBUTIONLISTS FOR DOCUMENTS YOU DON'T NEED!

TOTAL NUMBER OF COPIES REQUIRED:

LTTR 18 ENCL 17

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Arizona Public Service Company P.O. BOX 53999

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PHOENIX, ARIZONA85072-3999 WILLIAML. STEWART EXECUTIVEVI0 E PR ESI 0 ENT NUCLEAR 102-03278-WLS/AKK/GAM March 9, 1995 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Mail Station P1-37 Washington, DC 20555

References:

1)

Palo Verde Nuclear Generating Station (PVNGS), Unit 2 Facility Operating License, No. NPF-51, dated April 24, 1986 2)

Letter No. ANPP-37162, dated June 26,

1986, "Item 3.b of Attachment 1

to Operating License NPF-51,"

from E. E. Van Brunt, Jr., ANPP, to G. W. Knighton, USNRC 3)

NUREG-0857, Safety Evaluation Report (SER)

Related to the Operation of PVNGS Units 1, 2, and 3, Supplement 11, dated March 1987

Subject:

4)

Letter dated July 1, 1994, "Staff Evaluation of the Palo Verde Nuclear Generating Station Individual Plant Examination (IPE) for Internal Events" from B. E. Holian, USNRC, to W. L. Stewart, APS Palo Verde Nuclear Generating Station (PVNGS),

Units 1, 2, and 3 Docket Nos. STN 50-528/529/530 Charging System/Auxiliary Pressurizer Spray System Commitments File: 95-056-026. 95-186-419 In the Reference 2 letter, APS committed to implement several modifications to the charging systems in each PVNGS unit, as identified below.

APS has reevaluated the committed modifications and concluded that the proposed modifications should not be implemented because they would not provide a safety benefit commensurate with their costs and they are not needed to meet licensing requirements.

This action is being submitted as a cost beneficial licensing action (CBLA). Further discussion is provided below and in the enclosed engineering evaluation.

License Condition 3.b of Attachment 1 to the PVNGS Unit 2 Operating License (Reference

1) required APS to submit an evaluation and implementation schedule regarding a long-term solution to the concern of gas binding the charging pumps which considered alternative hardware changes that may be necessary to eliminate the need 9503160316 950309 PDR -ADOCK'05000528 P

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U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Charging System Commitments Page 2 for venting hydrogen from the suction ofthe charging pumps. The charging system, part of the chemical and volume control system, can be used to provide auxiliary pressurizer spray to reduce reactor coolant system pressure during natural circulation conditions.

In the Reference 2 letter, responding to that License Condition, APS submitted the results of an engineering evaluation proposing the following modifications to the charging system:

(1)

Provide train B of Class 1E power sources to the existing boric acid makeup pumps (BAMPs).

(2)

Provide train B of Class 1E power sources to the BAMP discharge line isolation valve (CH-514) connecting the charging pump suction header.

(3)

Install a new volume control tank (VCT) outlet isolation valve in series with the existing isolation valve (CH-501) for redundancy.

Electric power to the new isolation valve will be supplied from train B of Class 1E sources.

(4)

Cable installation for the above-stated power supplies will not be designed to meet safety-grade criteria.

However, proper isolation devices will be provided between the Class 1E power sources and the non-safety-grade electrical cables which supply power to non-safety-grade pumps and valve operators.

APS committed to implement these proposed modifications during the first refueling outage of each unit after one year following the final resolution of Unresolved Safety Issue (USI) A-45.

The NRC staff accepted the proposed modifications and implementation schedule in Section 5.4.3 ofthe SER Supplement 11 (Reference 3). USI A-45 was resolved in the PVNGS Individual Plant Examination (IPE), which received NRC approval in the Reference 4 letter dated July 1, 1994.

In order to ensure that expenditures of resources provide commensurate safety benefits, APS performed an engineering evaluation (enclosed) to reevaluate the proposed charging system commitments.

This evaluation includes probabilistic risk assessments of the charging system to compare the unavailability of the charging system with and without the proposed modifications.

The evaluation also addresses the ability of the current plant configuration to ensure cooldown and depressurization of the reactor coolant system with loss of offsite power to comply with Branch Technical Position RSB 5-1.

The enclosed engineering evaluation concludes that although implementing the proposed modifications would provide a small increase in charging system reliability as calculated by PRA, there would be virtually no effect on the overall plant core damage frequency.

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U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Charging System Commitments Page 3 The safety benefit is conservatively estimated in economic terms to be $16,200, while the cost is estimated at $8,600,000. Additionally, because of demonstrated system reliability, operator training and procedural controls to vent the charging pumps if necessary, and the availability of an alternative method to depressurize the RCS using the reactor head and pressurizer vent paths, all licensing requirements are currently met. Based on these conclusions, APS requests NRC concurrence to not implement these committed charging system modifications. APS plans to remove the committed charging system modifications from the plant modification planning process.

Should you have any questions, please contact Scott A.

Bauer of my staff at (602) 393-5978.

Sincerely, WLS/SAB/8AM/rv Enclosure cc:

L. J. Callan K. E. Perkins B. E. Holian K. E. Johnston

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